Income Taxes (Details 2) (USD $)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Capital losses
Deferred tax asset resulted from capital losses	$ 2,358,000	$ 2,577,000
Deferred income tax assets resulting from non-capital loss carryforwards	18,434,000	8,451,000
Potential interest and penalties associated with uncertain tax positions
Potential interest and penalties associated with uncertain tax positions	0	0	300,000
Deferred income tax assets:
Risk management liabilities	33,386,000	8,904,000
Non-capital loss carry forwards	18,434,000	8,451,000
Deferred charges	6,890,000	1,166,000
Capital losses	2,358,000	2,577,000
Other	2,403,000	806,000
Total	63,471,000	21,904,000
Valuation allowance	(4,004,000)	(2,607,000)
Total deferred income tax assets	59,467,000	19,297,000
Deferred income tax liabilities:
Property, plant and equipment	114,298,000	114,148,000
Intangible assets	15,137,000	17,636,000
Partnership deferral income	37,499,000	11,007,000
Risk management assets	17,049,000	11,477,000
Other	535,000	267,000
Total deferred income tax liabilities	184,518,000	154,535,000
Net deferred income tax liabilities	125,051,000	135,238,000
Deferred income tax liabilities:
Current	5,678,000	14,303,000
Long-term	119,373,000	120,935,000
Net deferred income tax liabilities	125,051,000	135,238,000
Changes to the Company's unrecognized tax benefits
Balance at the beginning of period	1,160,000	3,267,000
Additions based on tax positions taken in the current year	375,000
Additions (reductions) based on tax positions taken in a prior year	200,000	(1,411,000)
Settlements with taxing authorities in the current year		(696,000)
Balance at the end of period	1,735,000	1,160,000	3,267,000
Unrecognized tax benefits that would have an impact on the effective tax rate if subsequently recognized	1,700,000
Canadian subsidiaries
Capital losses
Accumulated non-capital losses	76,200,000	34,900,000
Deferred income tax assets resulting from non-capital loss carryforwards	18,400,000	8,500,000
Deferred income tax assets:
Non-capital loss carry forwards	18,400,000	8,500,000
Canadian subsidiaries | Capital losses
Capital losses
Capital losses	18,900,000	20,600,000
Deferred tax asset resulted from capital losses	2,400,000	2,600,000
Amount of capital losses offset by valuation allowance	2,400,000	2,300,000
Amount of tax assets related to losses expiring at the end of 2029	100,000
Deferred income tax assets:
Capital losses	$ 2,400,000	$ 2,600,000